Composite dipole multi-channel television antenna



1956 J. F. GUERNSEY ETAL 2,772,413

COMPOSITE DIPOLE MULTI-CHANNEL TELEVISION ANTENNA Filed. March 30, 1956 5 Sheets-Sheet 1 jnvewim 1956 J. F. GUERNSEY ETAL 2,772,413

COMPOSITE DIPOLE MULTI-CHANNEL TELEVISION ANTENNA Filed March 30, 1956 5 Sheets-Sheet 2 affair-45 1956 J. F. GUERNSEY EI'AL 2,772,413

COMPOSITE DIPOLE MULTI-CHANNEL. TELEVISION ANTENNA Filed March 30, 1956- 5 Sheets-Sheet 5 W ilmli z vezziil/"l M6 6716 6 @W L J Nov. 27, 1956 J. F. GUERNSEY EIAL 2,772,413

COMPOSITE DIPOLE MULTI-CHANNEL TELEVISION ANTENNA V Filed March 30, 1956 5 Sheets-Sheet 4 1%.; wean/w: e

NW 11 5 J. F. GUERNSEY Em 2,11

COMPOSITE DIPOLE MULTI-CHANNEL TELEVISION ANTENNA 5 Sheets-Sheet 5 Filed March 30, 1956 United States Patent CUD/IPOSITE DIPOLE MULTI-CHANNEL TELEVISHON ANTENNA John F. Guernsey and Arthur E. Vail, Griggsville, lll., assignors to Trio Manufacturing (30., Griggsville, 111., a corporation of Illinois Application March 30, 1956, Serial No. 575,153

18 Claims. (Cl. 343--801) This invention relates generally to high frequency antennas, and more panticularly is concerned with the construction of an antenna whose specific, although not exclusive purpose, is the reception of television signals over the presently known television spectrum in the so-called low and high channels, as opposed to the ultra-high fre quency channels. The presently utilized channels of television signal transmission are in two bands designated low consisting of channels 2 to 6 inclusive and high consisting of channels 7 to 13 inclusive. The range of frequencies for the low band are 54 to 88 megacycles per second and for the high band are 174 to 216 megacycles per second.

Although the description and discussion which follows hereinafter are specifically directed to the construction and operation of an antenna for the reception of television signals of the particular bands now available, it is not intended that the invention will be limited thereby. The antenna is operative with identical advantages in transmission as well as in reception and on other parts of the radio wave spectrum, for example by amateurs and for commercial and experimental use. Practically, of course, the transmission of television signals is accomplished by omni-directional single frequency antennas, and commercial transmission is usually accomplished on much less than twelve different frequencies from the same antenna.

A television antenna intended for reception of all signals available in a given location is required to receive transmitted signals in both of the available bands. In rural or fringe areas, the strength of signal requires antennas to have higher gain than in metropolitan areas where the signal strength of the transmitting stations is high. Broad band reception is required, and in the design and construction of television antennas many compromises must be made to meet the requirements of the user. Broad band reception usually goes hand in hand with low gain. High gain antennas are usually highly directive. An antenna which is efficient in the low band will usually be inefficient in the high band, and vice versa. Antennas with good reception qualities may have bad impedance characteristics so that the transfer of the signal to the receiver is inefficient.

Many problems are posed, as indicated by the statements made above, which do not completely set forth the difficulties which must be overcome in order to arrive at a structure which will provide high gain over the entire spectrum.

The construction of a high gain television antenna is further complicated by additional difficulties which might be summarized "by listing What is needed in order to give the purchasing public maximum of benefit with minimum of cost:

1. First, of course, the antenna must be universal, i. e., provide substantially uniform high gain over the entire spectrum so that any purchaser in any area of the country may obtain good reception without the need for adjustment of the antenna other than at the time of installation, and then only as to direction. reception requires uniform gain also.

2. The antenna must occupy small volume and be made up of light weight elements so as not to be diflicult to install, transport, and so that mounting is no problem due to weight.

3. The antenna must present as little resistance as possible to the wind and weather so that it may be expected to remain properly oriented if permanently affixed, or it may be expected not to place strain upon the mounting if rotatively affixed-and in any event so that it will not be blown down.

4. The antenna should be constructed in such a mannor as to be foldable to admit of easy packaging, and be capable of assembly quickly and with a minimum of tools, any.

5. The antenna must be capable of fabrication in production line methods to enable economy to be passed on to the purchasing public.

The principal object of this invention is to provide a high frequency antenna for the reception of signals over a wide spectrum with high gain and with the advantages enumerated above, many of them achieved because of the inherent structure of the antenna and others achieved because the construction permits of the same.

Still another object of the invention is to provide a novel composite dipole structure of the so-called end-fire type which has high gain and broad band characteristics not heretofore believed possible of achievement with an antenna of this type.

Another object of the invention is the provision of an array of composite modified end-fire dipoles so arranged in a single plane as to result in high gain over all the television channels between 2 and 13.

Still a further object of the invention is the provision of an antenna which includes, in addition to the composite dipole array, a novel arrangement of parasitic elements, increasing the gain and the rejection of backreceived signals.

An important object of the invention lies in the provision of novel structure of the composite dipole elements of the antenna to enable them readily to be folded for transportation and storage.

Many other objects of the invention will become apparent as a description thereof proceeds, in connection with which preferred embodiments have been illustrated in drawings accompanying this specification, in order to make known the manner of construction and use of the invention.

In connection with the description, the nature of the theory of operation of the antenna of the invention will be alluded to, but this is only by way of a desire to assist in the understanding thereof and not by way of lim'ivta tion. Whether the theory of operation is correct is immaterial, it being of prime impontance that the structure described, illustrated and claimed performs the functions desired with outstanding and greatly improved results.

in the drawings, in which the same characters are used throughout the several figures to designate the same or similar parts:

Fig. 1 is a bottom perspective view of an antenna array for use on the television channels, composed of three driven composite dipoles constructed according to the invention and phased together to give maximum beneficial signal, the remaining elements of the antenna array being parasitics.

Fig. 2 is a similar view of an antenna array also for television use, in which there are only two driven composite dipole elements, the remaining elements being panasitt-ics.

Fig. 3 is a perspective view of a single active com- Good color posite dipole element, constructed in accordance with the invention.

Fig. 4 is an enlarged bottom plan view of a portion of the antenna of Fig. 2 showing the manner of connecting the phasing harness and the transmission line to the receiver.

Fig. 5 is a view similar to that of Fig. 4 but of the antenna of Fig. 1.

Fig. 6 is a sectional view through the antenna of Fig. 1 taken along the line 6-6 of Fig. 5 and in the indicated direction.

Fig. 7 is a fragmentary top plan view of one of the composite dipoles of the invention showing the details of construction which enable the composite dipole to be folded substantially parallel with the boom.

Fig. 7a is a diagram used in explaining the folding of the composite dipole of Fig. 7.

Fig. 8 is a view similar to that of Fig. 7 but showing the composite dipole in folded condition.

Figs. 9, 10, 11, 12 and 13 are views showing the details of mechanical construction of the antenna of the invention, Fig. 9 being a sectional view through the composite dipole mounting of Fig. 7 on line 99, Fig. 10 being a top plan view of a parasitic element mounting and Figs. 11 and 12, sectional views therethrough, and Fig. 13 is a section through a clamp (Fig. 7).

Figs. 14, 15, 16, 17 and 18 are diagrammatic views used for explanatory purposes in describing the theory of operation and showing how the construction of the composite dipole of the invention is derived.

Referring first to Fig. 3 there is illustrated an antenna which has herein been termed a composite dipole and which will be designated by the character D. The composite dipole D is mounted on the boom 20, which in eventual disposition is arranged horizontally, by means of two brackets designated generally 22 and 24. Details of the brackets will be reserved for another portion of this specification. The front of the composite dipole D, that is the direction of maximum signal gain is indicated by the arrow parallel with the boom 20.

The front part of the composite dipole D is formed of three elements, the outboard elements 26 and the inboard element 28. Following the chosen designation of direction, the inboard element 28 being formed of two halves meeting at the bracket 24, these halves are designated 28-R and 28-L, for right and left (looking from rear to front of the composite dipole D). Likewise the outer elements are designated 26R and 26L. Each element 26 and 28 has substantially the same electrical length, but it will be noted that the elements are connected by insulating members 30-R and 30L electrically separating the elements. For this purpose clamps 32-R, 32L, 34R and 34L are provided. In the practical example 28 is a few percent longer than 26R or 26L which are equal, for a reason which will appear.

The clamps 34-R and 34-L each pivotally mount a rearwardly and inwardly extending link or connector designated respectively 36-R and 36-L which electrically connect the outboard elements 26 with the ends of a fourth element 38. The element 38 has right and left halves 38-R and 38-L which meet at the bracket 22, spaced rearwardly along the boom 20 from bracket 24. The electrical length of element 38 is substantially the same as the electrical length of elements 26R and 26L. Thus, if the elements 26R, 26-L and 38 each consist of a dipole resonant for a frequency f3, then together the connected dipoles form a single dipole resonant for a frequency f1 which is one-third the frequency f3.

In the present-day frequency spectrum, the centers of the two bands have an approximate one to three frequency relationship, and hence the convenience of using such a composite dipole element as D for the two bands is apparent.

The composite dipole D has elongate diagonal elements 40R and 40-L connecting the extreme outer ends of the outboard elements 26R and 26-L respectively with the bracket 22. This is a mechanical connection insofar as bracket 22 is concerned since the ends of diagonal elements 40-R and 40-L form terminals for driving the composite dipole D and hence are insulated from the boom 20. By driving it is meant that the antenna is connected with a transmission line, for connection either to a transmitter or a receiver. Obviously, where the antenna is a television receiving antenna, the composite dipole D will be connected with a television receiver.

The construction of brackets 22 and 24 will be described hereinafter in connection with Figs. 7, 8, 9. Suffice it to say at this time that the bottom of bracket 22 has an insulator block thereon, and the ends of the diagonal elements 40-R and 40-L are connected to the block, from whence either transmission line or phasing harness terminals, or both, may be connected.

The diagonal elements 40-R and 40L are integral continuations of the outboard elements 26R and 26L respectively, being joined thereto by means of the bends 41-R and 41-L respectively. It will be noted that the free ends which are designated 42-R and 42-L extend from a level on the topside of the boom 20 to a level below the boom and spaced rearwardly of the bends 4141 and 41-L so that the elements of the composite dipole D are not actually co-planar. The diagonal elements are somewhat twisted downward and backward. It is desired to point out, however, that this is a matter of practical construction and not an electrical requirement of the dipole. The elements of the dipole could satisfactorily and desirably be in substantially a horizontal plane.

The described construction of a single composite dipole D illustrates that the antenna is disposed anything but broadside to the wind, so that the principal stress from wind is reduced over other antennas of collinear type which have a plurality of elements in vertical planes.

The function of the diagonal members 40-R and 40L is not only to provide support for the antenna, but as well to increase the terminal impedance for a better match to the usual transmission lines of approximately 300 ohms terminal impedance. Thus, the composite dipole D may be considered a folded dipole structure.

The composite dipole element D may be termed a modified, end-fire, folded, unidirectional element for reasons presently to be pointed out. For the discussion which follows, attention is invited to Figs. 14, 15, 16, 17 and 18 in connection with which an attempt will be made to explain a likely theory of operation of the antenna.

Figs. 14 and 15 represent the known form of end-fire alfitenna. Considering a pair of parallel collinear arrays 0 length, made up of three simple dipoles each comprising A1, A2, A; and B1, B2, B3, if the center dipoles of the arrays are interposed and each array fed from a common transmission line, the arrays will be in phase. Current distribution will he as indicated by the broken line diagrams la 1A 1A IE IE3, I13 The instantaneous direction is as indicated by the arrows in Fig. 15.

The transposition of center dipole A2 and B2 is accomplished by cross-connecting links G and H. The phase of the collinear arrays is reversed by a transposition of the terminals of the center elements through the medium of a connecting cross-over harness C, and the correct phase relationship of antenna arrays one to the other depends on the spacing S. The transmission line Xmn is thus connected at a point FF which takes this into account.

It will be recalled that the phase of a given wave front will necessarily change from the time that it is intersected by the front collinear array until the time that it reaches the second collinear array, and the amount of change is a function of the frequency and the distance S, or in other words, the distance in wave length from the front to rear collinear arrays. This demonstrates the need for the adjusted connection of the transmission line. Close spacing of the arrays gives best gain. (The spacing of the practical example D is approximately to s Where is the frequency at which any of the elements 26 or 28 is a dipole.)

The characteristics of the end-lire antenna of Figs. 14 and 15 are not suitable for television reception because the radiation pattern, while fairly narrow, is the same front and back, and the antenna is suitable for use on only one frequency A or at best x and 3A although phasing between arrays is not suitable on the latter frequency.

It was discovered that by de-coupling one array completely, and center feeding the other array, an unusual and not contemplated result was obtained. instead of being bi-directional the dipole element became unidirectional, giving an excellent forward radiation lobe L1 in the direction from which the cle-coupled center section B2 is the front of the antenna and small rear minor lobes L2 oil center. There being no direct coupling between arrays, there is no need for coupling harness CC, and the antenna may be fed at the center of the dipole A2. Instead of being a single frequency antenna, the resulting structure had excellent broad characteristics over the entire spectrum of the television high-band and gave good results over the low-band. Impedance-wise the assemblage had a terminal impedance of the order of 300 ohms on the high band, but of considerably less on the low band. By adding the diagonal elements 4ill and i t'i L the antenna appeared as a folded dipole on the low band and hence the terminal impedance for those frequencies was substantially increased to approximately 300 ohms Without materially affecting the antenna characteristics on the high band frequencies.

Of importance and considerable additional improvement over the ordinary end-fire antenna is the lack of criticality of the dimensions of the driven elements A1, A2 and A3 which are respectively the dipoles 26R, SS-R and 38L, and 26-L in the practical embodiment, diagrammed in Fig. 18. The diagram of Fig. 16 is an intermediate stage of the antenna between the end-fire antenna of Fig. 15 and the preferred example of Fig. 17. The difference lies in the elimination of the cross connecting members H whereby greater decoupling of the elements B1, B2 and B3 from the driven elements A1, A2 and A is accomplished.

It will be appreciated that the elements B1, B2 and B3 appear to be parasitics in that they are fully disconnected metallically from the driven elements and the trans mission line Xmn. However, their spacing and inter position between elements A1, A2 and A3 is such that there may be some nature of coupling not inconsistent with the usual understanding of the operation of parasitics. In choosing the dimensions of the elements B1, B2 and 13 if the dimensions of the driven elements are chosen to be dipoles for the center of the high band, say channel it), and the elements B1, B and B3 are handled as parasitics, best results are obtained. B1 and B being to the rear of the elements A1 and A3 respectively are made reflectors for channel 7, the low end. B2 being in front of element A2 is made a director for channel 13, the high end. The final result was that all of the so-called parasitic elements B1, B2 and 133 were somewhat longer than the respective elements A1, A2 and A3.

The dipole D represents an economical variation of the preferred structure in which the elements B1 and B3 are eliminated. An antenna which uses these elements, properly supported and cut to the lengths described above, will give increased gain-up to 2 db on the high band frequencies. This gain must be weighed t 6 against the increased cost of mass producing such antennas.

In. Fig. 18, the resulting current distribution of the practical dipole D is shown, with the high band current represented by solid lines and the low band represented by broken lines. The arrows indicate instantaneous direction.

The antenna described may be used by itself, that is, benefits of the invention are achieved through the application of the composite basic dipole D for reception or transmission of high frequency signals. Obviously, pattern and gain are improved by stacking and multiple arrays. In utilizing the composite antenna element D, however, several combinations of composite dipoles with systems of parasitics have given excellent results for reception of television signals over all channels of high and low bands.

In Fig. 2 there is illustrated an antenna 50 which has two driven composite dipoles D1 and D2 of the identical construction as the composite dipole D, coupled together by a phasing harness 52 which is in turn connected at 54 to the transmission line 56. There are five parasitic elements which are designated from front to rear 53, 59, 6h, 61 and 62. All elements are mounted on a horizontal boom 20 which is supported on a vertical mast M by means of a suitable clamp 66. All of the parasitic elements are supported at their centers by identical metallic brackets 64% and the supports for the dipoles D1 and D are brackets identical to 22 and 24 already mentioned. Details of brackets 63 will be given below in connection with Figs. 10, 11 and 12.

The elements 58 and 6t) serve as directors for the high band frequencies. Each is formed of three short side-by-side elements 53-R, 5SM, 5%L and sea, 604%, oft-L, respectively. The separation between short elements being effected by lengths of insulating material 35} identical with the lengths Ell-R and 3tlL of composite dipole D, held in place by clamps 32 substantially identical to clamps 32-R and 3ZL of composite dipole D. As will be explained, the middle sections 58-M and titLM, fold in two to permit collapse of the antenna.

Element 59 is operative as a director in the low band. It also folds in the center.

Elements 61 and 62 serve as low band reflectors and at least element 61 serves as a high band reflector.

The array described gives extremely high gain and directivity, over all channels of the television bands, using the basic characteristics of the composite dipoles D1 and D2 enhanced by Yagi principles. With proper choice of dimensions the two composite dipoles D1 and D2 not only give twostep broad coverage over the bands, but also complement one another as parasitic reflector or director as the case may be through proper spacing and phasing.

Reference now will be made to Fig. 4 which is a fragmentary bottom plan view of the antenna 5t) showing the two driven composite dipoles D1 and D2 connected to be in proper phase so that both may feed the transmission line 56. The bracket 22 is of metal except for the bottom insulator member 7t) and the inner ends of the members 33-1. and 38R being pivotally mounted on the bracket 22 by metal rivets, as will be described, establishes electrical connection between the boom 20 and the members 38R and 38L. Since the potential at the center of the dipole 38 is substantially zero, this is of no consequence. Likewise, the parasitic dipole 23 is mounted with the inner ends of the halves ZS-R and 28-L metallically connected to the boom Ztl through bracket 24.

The ends 42R and 42-L of the diagonal members: MFR and 4tlL respectively are flattened and connected to binding posts 54 provided on the insulator 70. The terminals of the transmission line 56 of the antenna 50 are also connected to these binding posts 54 of the composite dipole Dz toward the rear of the antenna. The composite dipole D1 has identical construction enabling the mounting of the same, although its dimensions are somewhat smaller than composite dipole D2 so that it covers a somewhat different range of frequencies, albeit overlapping. The binding posts 54 of its bracket 22 serve as terminals for the phasing harness 52, the other terminals of which are the binding posts 54.

The phasing harness is a pair of wires or metal conductors 72 and 74 which comprise a transmission line and are spaced from one another and from the boom, and extend parallel between the dipoles D1 and D2, for con venience being disposed on the top of the antenna above the boom 26. The ends of the wires 72 and 74 are bent in loops 72 and 74 which extend downward and around the brackets 22 and 24, clearing the brackets, parts of the dipoles and the boom to enable the connection to the binding posts 54 and 54.. The ends are preferably bent into eyes to provide good securement, and insulating spacers 76 may be provided along the length of the harness 52. The length of the harness is sufficient to adjust the phasing between composite dipoles D1 and D2 so that they will augment and complement one another on all frequencies. Thus, when not serving as a driven element, the dipole will be a parasitic for its mate.

Much better results, that is to say more uniform and higher gain over the high and low television bands is obtained with an antenna 80 illustrated in Figs. 1, and 6. As in the case of previously described antennas this is a modification in which composite dipoles similar to D are used having elements which exclude B1 and B; because of practical reasons.

The antenna 89 is mounted on a boom 20 and supported upon a vertical mast 64 by a clamp 66 of any suitable design. The driven elements of the antenna are three in number, and are designated D3, D4 and D5 commencing with the foremost element. All are substantially identical in construction to the element D and are chosen to cover the entire spectrum of high and low bands of the television spectrum in three ranges instead of two. The frequencies for which the composite dipoles D3, D4 and D5 are cut decrease from front to rear of the antenna, and phasing harnesses 82 and 84 are provided of substantially the same construction as the phasing harness 52, for connecting the three driven elements in proper phase.

The elements of the antenna include, in addition to the driven ones, an integral rear reflector as, which serves the low band; an intermediate high band element 88 and two composite parasitic elements 9%) and 92. These latter two antennas serve as directors on high and low bands. The foremost of these, namely 92, is the smaller. Otherwise, they are the same in construction. Considering element 99 (see Fig. 5) metallic brackets substantially identical to the brackets 24 are mounted on the boom Ztl, spaced apart a suitable distance, and properly arranged relative to the dipoles D3, D4 and D5. A rear high band parasitic element 92 is mounted on the rear bracket and a front high band element 94 is mounted on the front bracket 24. The outer ends of the front high band element 94 are connected with diagonal elements 96 (designated 96R and 96-L in association with the respective element halves 92-R94-R and 9ZL 94L). The connection is achieved through insulating members 3t)R and 30L and clamps 32-R and 32-L.

There is a metallic connection between the elements 92, 94 and 96 and the boom, since all are parasitics. The ends of 96R and 96L may be secured to the rear bracket 24 by thumb nuts, for example, as at 98-R and 98-L, to aid in folding the composite assemblage 96).

On high frequencies, it is believed, the outboard portion HNLR and 1tlllL are of a phase cancelling the effect of the aligned outer portions of the slanted elements 96R and 96-L thus providing in effect a high band parasitic element in addition to elements 92 and 94. On low frequencies, it is believed, the elements 92, 94 and the parts 190R and mil-L have no effect upon the action of the slanted portions alone combining to form a veed forward parasitic element.

The intermediate element 88 acts either as a reflector for high band elements in the composite dipole D3 or as a director for high band elements in composite dipoles D4 and D5 depending upon the frequency at which the antenna 80 is being operated.

he harnesses 34 and 82 are mounted as best shown in Fig. 6. The harness 84 with its intermediate spacers 76 is above the boom 20 (to the right as seen in Fig. 6) and its ends 104 and 106 curve around and down to be connected respectively to the binding posts of the brackets 22 and 22" which are identical in construction to bracket 22. The harness 82 is disposed on the bottom of the antenna and its ends 108 and 110 respectively curve around and upward and are secured respectively to the binding posts of the brackets 22 and 22. Each of the brackets 22, 22" and 22" has the same insulator 70 referred to, and the binding posts are identical with binding posts 54 to conductively tie the diagonal elements 40 of the dipoles in parallel, properly phased and fed by the transmission line 56' which is also con nected to the rear bracket 22.

it is not believed necessary to describe the remaining details of the antenna 80, since in. all other respects its parts are identical with parts already described.

Considering Figs. 7, 8, 9, 10 and 11 the structure which enables the antenna to be folded for shipment in narrow cartons, and which enables easy erection is illus trated. This structure is common to all of the composite dipoles D, D1, D2, D3, D4 and D5. The half of the composite dipole D which includes the elements 38-L, 28L, and 36-L is a trapezoid. For ease in assembly without tools, the four corners of the trapezoid (as do all others) are permanently secured by pivotal rivets or pins 112, 113, 114 and 115. The pin 112 passes through the protective end cap 116 and flattened end of the element 38L and is secured to the base 118 of the bracket 22. An upwardly biased leaf spring 120 having a seating slot 122 is adapted to ride the outer formed channel 124 of the cap 116 to snap the element 38-L into position normal to the boom 20 when moved from the folded position of Fig. 8 to the extended position of Fig. 7. The spring 120 must be forced away from the cap 118 to permit folding, if desired, but this is some what diflicult, since the extended condition of the elements is intended to be permanent.

The element 28-L is secured to the bracket 24 by rivet or pin 1 15 in the same manner. There is a cap 116, a base 118, a spring 1 20', a slot 122, a channel 124' all of which function the same as the elements similarly designated but unprimed.

The connecting link 36L is formed of two parts 126 and 128 permanently pivoted at 130 intermediate the ends which connect between link 38-L and 26L. In order that the trapezoidal formation be foldable so that the entire element D is capable of being disposed substantially parallel with and alongside the boom 20, the various lengths of the elements must be properly proportioned. This is done by choosing the position of the pivot 30 so that the distance from pivot 115 to pivot 114, plus the distance from pivot 114 to pivot 130 is equal to the sum of the distance from pivot 115 to pivot 112 plus the distance from pivot 112 to pivot 113 plus the distance from pivot 113 to pivot 130. In other words, as indicated by diagram of Fig. 7a, a|b+c=d+e. When this condition is met, at least substantially, the folding of the element D can be accomplished. The diagonal elements 40-R and 40L have their end 42-R and 42L perforated, and these ends must be disconnected from the binding posts 54 to permit folding but are reconnected when the composite dipole is extended.

It will be noted that the bracket 22 has the metallic base 118 mounted to the boom 20 by a long bolt or rivet 114 which secures the insulator 70 on the bottom, but electrically independent of the base 118 so that the binding posts 54 connect metallica'lly only with the elements 4ti-R and 40-L and such harnesses and transmission lines as may be secured thereto by the thumb nuts 142.

The facing caps 1'16 and 1 16 of the brackets 22 and 24 have cooperative diagonal facing ends 146 and 146 which engage to provide a locking engagement providing alignment of oppositely extending elements. Obviously one side must be folded or extended before the other.

Bracket 68 comprises a metal base 150 riveted to the boom Ztl and having a resilient cover plate 152. The elements such as, for example, 62-R and 62-L are pivoted to the base at 154 and the base has upwardly struck inwardly extending lugs 156 forming pockets with slanted sides into which the elements 62-R and 62L are readily snapped but out of which the elements cannot be rotated without substantially distorting the parts. Obviously other brackets permitting folding of the parasitic elements can be used.

Fig. 13 illustrates the clamp 32 which is a tubular member crim-ped around the ends of metallic elements with insulating rod in the center. Any crimping or clamping means can be used.

In order to provide sutficient information to enable one skilled in the art to construct the antennas of the invention, the practical embodiments for use in receiving television signals on the present channel have been set forth hereinafter for the antenna 80. Adaptation for the antenna 50 is readily capable of being accomplished.

Composite dipole D3 is resonant at channel 6 and channel 13.

Inches Length of 28 end to end 23.5 Length of 38 end to end 21 Length of til-L (or 40-R) 32.75 Length of 26L (or 26-R) 19.25 Length of Fail-L (or 30R) 2 Front to rear width (S) 6.5

Composite dipole D4 is resonant at channel 4 and channel 10.

Inches Length of 28 end to end 26 Length of 38 end to end 25.5 Length of 4tlL (or Mi-R) 40.5 Length of 26-L (or 26-R) 25.75 Length of Mil-L (or 30R) 2 Front to rear width (S) 6.5

Composite dipole D5 is resonant at channel 2 and channel 7.

Inches Length of 28 end to end 31 Length of 38 end to end 30 Length of 49-1. (or 40-R) 48.5 Length of 26L (or 26-R) 31.25 Length of 30-L (or 30-R) 2 Front to rear width (S) 6.5 Overall length of harnesses:

82a; 38 84 38 Distance between D3 and D4 19.5 Distance between D4 and D5 19.5 Distance between D and 90 9.75 Distance between 90 and 92 16.5

Parasitic Inches Length of 94 end to end 24.5 Length of 92 end to end 24.5 Length of -L (or 100R) 10.5 Length of 96-L (or 96R) 25 Length of 30-L (or 30-R) 1 Parasitic 92 This element may either be the same size as element 92 or proportionally smaller, as for example, to resonate at slightly higher frequencies.

Inches Overall length of parasitic 88 26 Overall length of parasitic 86 Distance from D5 to 86 32.5 Distance from D4 to 88 6.5

It is believed that the invention has been sufiiciently described to enable one skilled in the art to understand, use and construct the same. The dimensions given have not included the lengths of the elements 36 and their parts, but these are easily computed from the specification. The antenna resulting from the invention is an array which to all intents and purposes is disposed in a horizontal plane and hence presents very little resistance to wind and produces very little moment upon the mast 64. The gain of the antenna over the entire spectrum is quite high and uniform. On channels 2 to 6 the directivity of the antenna is quite high, there being a front to back ratio of between 15 and 26 db, with no side lobes. On the high channels there are very minor side lobes, but the front to back ratio is still quite high. Considerable variation in these dimensions is well within the purview of the invention, and indeed such variations are made from time to time in the practical production of the antennas. For example, the distances between D3 and 90, and 90 and 92 may both be approximately 13 inches. Optimum dimensions may also vary from location to location, but importantly, a great deal of criticality inherent in high gain antennas has been eliminated by the structure of the invention.

Parasitic configurations of other types may be used.

What it is desired to secure by Letters Patent of the United States is:

1. A composite antenna for high frequency signals comprising a plurality of dipole elements all arranged in substantially a horizontal plane, there being three collinear dipole elements and the antenna being highly directive along an axis normal to the collinear dipole elements, a fourth dipole element centered on the said axis spaced from and parallel with the middle one of the three collinear dipole elements, the four dipole elements being substantially of the same electrical length, the said middle dipole element being a director parasitic relative said fourth dipole element and the two outboard collinear dipole elements having their inner ends electrically connected to the ends of the fourth dipole, and transmission line means connected to drive the two outboard collinear dipole elements and the fourth dipole element.

2. A composite antenna as claimed in claim 1 in which there are two additional dipole elements collinear with said fourth dipole element but arranged outboard thereof and each a reflector parasitic relative the respective first mentioned outboard collinear dipole elements.

3. A composite antenna as claimed in claim 1 in which there is a fifth dipole element, but having an electrical length substantially three times the electrical length of said four dipole elements, said fifth dipole element being slightly veed with its outer ends connected to the outer ends of the outboard collinear dipole elements and its center disposed substantially at the center of the fourth dipole element, said center of the fifth dipole element being connected with said transmission line means.

4. A composite antenna as claimed in claim 1 in which 11 the spacing between the first mentioned three collinear dipole elements and the fourth dipole element is approximately one-fourth the electrical length of the dipole elements.

5. A composite antenna as claimed in claim 3 in which the spacing between the first mentioned three collinear dipole elements and the fourth dipole element is approximately one-fourth the electrical length of the dipole elements.

6. A composite antenna for high frequency signals adapted for high directivity unilaterally, comprising a metallic horizontal boom coaxial with the direction of directivity, a first dipole element normal to the boom and in a horizontal plane and metallically connected at its center with the boom, second and third dipole elements of substantially the same electrical length as the first dipole element arranged outboard thereof and collinear therewith and slightly spaced from the outer ends of the said first dipole element, insulating means mechanically connected between each of the outboard elements and said first dipole element, a fourth dipole element parallel with the first dipole element in the same horizontal plane and spaced axially therefrom on the boom, having its center metallically connected to the boom, a metallic link between each of the outer ends of said fourth dipole element and the inner ends of the outboard dipole elements, and a pair of conducting members extending respectively from the outer ends of the outboard dipole elements to the boom at a point spaced axially along the boom from the said first dipole element, means insulatedly securing the pair of conducting members to the boom and insulated from one another, and transmission line means connected to the pair of conducting members.

7. A composite antenna as claimed in claim 6 in which the axial point at which the pair of conducting members is connected to the boom is substantially the same as the point at which the said fourth dipole element is connected to the boom but on the opposite side therefrom.

8. A composite antenna as claimed in claim 6 in which the said first dipole element is formed of a length to render same a parasitic element relative the said fourth dipole element.

9. A compo-site antenna as claimed in claim 6 in which the first and fourth dipole elements are each formed of halves and the halves are each pivotally mounted to the boom for swinging movement in a horizontal plane, the conducting members are adapted to be removably secured to the boom at said point, and the said metallic links are pivotally secured at their ends and foldable between said ends, whereby the entire antenna may be collapsed with all of the elements and the conducting members arranged generally parallel with and alongside the said boom.

10. A composite antenna as claimed in claim 6 in which the area subtended on each side of the boom by the boom, half of said first dipole element, an insulating means, a metallic link, and half of said fourth dipole element is trapezoidal in configuration, with the link forming the diagonal side of the trapezoid.

11. A composite antenna as claimed in claim 9 in which the area subtended on each side of the boom by the boom, half of said first dipole element, an insulating means, a metallic link and half of said fourth dipole element is trapezoidal in configuration, with the link forming the diagonal side of the configuration, the link being foldable at a pivot point such that the sum of distance measured between pivots of the first and fourth dipole half elements on the boom plus the distance between the pivots of the fourth dipole half, plus the distance along the link between the pivot with the fourth dipole element and the folding pivot point, equals the sum of the remainder distance along the link, plus the distance measured between the pivot point of the link and the outboard dipole element to the pivot of the first dipole half element with the boom,

12. A composite antenna as claimed in claim 6 in which each conducting member is integral with an outboard dipole element and there is an arcuate reverse bend connecting each conducting member with the end of one of the outboard dipole elements whereby the two contive along an axis normal to the collinear dipole elements, length of which is substantially three times the electrical length of the said four dipoles.

13. An antenna array which is formed of at least a pair of composite dipole assemblages, each assemblage being arranged in substantially the same horizontal plane spaced one from the other and parallel one relative the other, a common horizontally arranged boom having the dipole assemblages mounted thereon, means supporting the boom, and transmission line means driving the assemblages, each assemblage comprising a first dipole element mounted at its center on the boom and having second and third collinear dipole elements respectively insulatedly connected at the ends of the said first dipole element and mechanically supported therefrom, a fourth dipole element spaced from the first dipole element, parallel therewith and secured to the boom also at its center, a metallic link between each of the ends of the fourth dipole element and the respective inner ends of the said outboard dipole elements, a pair of rigid conductor elements having inner and outer ends, the outer ends being respectively connected with the outer ends of said outboard dipole elements, and the inner ends being insulatedly secured to said boom at the center of the said fourth dipole element, and said transmission line means being connected to said inner ends.

14-. An antenna array as claimed in claim 13 in which said transmission line means include a phasing harness between the inner ends of the rigid conductors of each of said dipole assemblages having a length for phasing the said assemblages additively.

15. An antenna array as claimed in claim 14 in which the physical dimensions of one assemblage are proportionally smaller than the physical dimensions of the other assemblage and the smaller assemblage is located forward of the other considering the maximum directivity of the array.

16. An antenna as claimed in claim 15 in which both assemblages are foldable to positions substantially parallel with the boom.

17. A composite antenna for high frequency signals comprising a plurality of dipole elements all arranged in substantially a horizonal plane, there being three collinear dipole elements and the antenna being highly directive along an axis normal to the collinear dipole elements, a fourth dipole element centered on the said axis spaced from and parallel with the middle one of the three collinear dipole elements, the four dipole elements being substantially of the same electrical length, the said middle dipole element being a director parasitic relative said fourth dipole element and the two outboard collinear dipole elements having their inner ends electrically connected to the ends of the fourth dipole.

18. A composite antenna for high frequency signals comprising a plurality of dipole elements arranged in substantially a horizontal plane, there being three collinear dipole elements and the antenna being directive along an axis normal to the collinear dipole elements, a fourth dipole element centered on the said axis spaced from and parallel with the middle one of the three collinear dipole elements, the four dipole elements being substantially of the same electrical length, the said middle dipole element being of length rendering same parasitic relative to said fourth dipole element and the two outboard collinear elements being coupled at their inner ends to the respective ends of said fourth dipole, said two outboard collinear dipole elements and fourth adapted to be connected to electrical energy transmission means.

(References on following page) References Cited in the file of this patent V Re. 23,960

UNITED STATES PATENTS Lorusso Mar. 8, 1955 Scharlau May 3, 1938 Carter Dec. 19, 1939 Alford Apr. 2, 1940 Scheldorf July 10, 1945 14 Kaplan Dec. 27, 1949 Clark July 22, 1952 Hillison Oct. 13, 1953 Collins et a1. May 4, 1954 Lo Oct. 12, 1954 Winegard Jan. 18, 1955 Thomas Mar. 29, 1955 

